from ryu.base import app_manager
from ryu.controller import ofp_event
from ryu.controller.handler import CONFIG_DISPATCHER, MAIN_DISPATCHER
from ryu.controller.handler import set_ev_cls
from ryu.ofproto import ofproto_v1_3

from ryu.lib.packet import packet
from ryu.lib.packet import ethernet
from ryu.lib.packet import ipv4
from ryu.lib.packet import ether_types

# SimpleSwitch13 is a simple learning switch
# This app Works on top of controller
class SimpleSwitch13(app_manager.RyuApp):
    OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]

    def __init__(self, *args, **kwargs):
        super(SimpleSwitch13, self).__init__(*args, **kwargs)
        self.mac_to_port = {}

    @set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
    def switch_features_handler(self, ev):
        datapath = ev.msg.datapath
        ofproto = datapath.ofproto
        parser = datapath.ofproto_parser

        match = parser.OFPMatch()
        actions = [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER,
                                          ofproto.OFPCML_NO_BUFFER)]
        self.add_flow(datapath, 0, match, actions, meter=None)

        bands = []
        dropband = parser.OFPMeterBandDrop(rate=200, burst_size=0)
        bands.append(dropband)
        request = parser.OFPMeterMod(datapath=datapath,
                                        command=ofproto.OFPMC_ADD,
                                        flags=ofproto.OFPMF_PKTPS,
                                        meter_id=1,
                                        bands=bands)
        datapath.send_msg(request)
        
    # add_flow is used to add new flow entry in flow table
    def add_flow(self, datapath, priority, match, actions, buffer_id=None, \
        meter=None):
        ofproto = datapath.ofproto
        parser = datapath.ofproto_parser

        if meter:
            inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS, \
                actions),parser.OFPInstructionMeter(1)]
        else:
            inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS, \
                actions)]

        if buffer_id:
            mod = parser.OFPFlowMod(datapath=datapath, buffer_id=buffer_id,
                                    priority=priority, match=match,
                                    instructions=inst)
        else:
            mod = parser.OFPFlowMod(datapath=datapath, priority=priority,
                                    match=match, instructions=inst)
        datapath.send_msg(mod)

    @set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
    def _packet_in_handler(self, ev):
        # If you hit this you might want to increase
        # the "miss_send_length" of your switch
        if ev.msg.msg_len < ev.msg.total_len:
            self.logger.debug("packet truncated: only %s of %s bytes",
                              ev.msg.msg_len, ev.msg.total_len)

        msg = ev.msg
        datapath = msg.datapath
        ofproto = datapath.ofproto
        parser = datapath.ofproto_parser
        in_port = msg.match['in_port']

        pkt = packet.Packet(msg.data)
        eth = pkt.get_protocols(ethernet.ethernet)[0]

        if eth.ethertype == ether_types.ETH_TYPE_LLDP:
            # ignore lldp packet
            return

        ip = pkt.get_protocol(ipv4.ipv4)

        dst = eth.dst
        src = eth.src

        dst_ip = ""
        src_ip = ""            
    
        dpid = datapath.id
        self.mac_to_port.setdefault(dpid, {})

        # learn a mac address to avoid FLOOD next time.
        self.mac_to_port[dpid][src] = in_port

        if dst in self.mac_to_port[dpid]:
            out_port = self.mac_to_port[dpid][dst]
        else:
            out_port = ofproto.OFPP_FLOOD


        actions = [parser.OFPActionOutput(out_port)]

        # install a flow to avoid packet_in next time
        if out_port != ofproto.OFPP_FLOOD:
            if (ip):
                dst_ip = ip.dst
                src_ip = ip.src
                match = parser.OFPMatch(in_port=in_port, eth_dst=dst, \
                    eth_src=src, eth_type = 0x0800, ipv4_dst = dst_ip, \
                        ipv4_src = src_ip)
            
            else:
                match = parser.OFPMatch(in_port=in_port, eth_dst=dst, \
                    eth_src=src)
            
            # verify if we have a valid buffer_id, if yes avoid to send both
            # flow_mod & packet_out
            if msg.buffer_id != ofproto.OFP_NO_BUFFER:
                self.add_flow(datapath, 1, match, actions, msg.buffer_id, \
                    meter = True)
                return
            else:
                self.add_flow(datapath, 1, match, actions, meter = True)

        data = None

        if msg.buffer_id == ofproto.OFP_NO_BUFFER:
            data = msg.data

        out = parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id,
                                in_port=in_port, actions=actions, data=data)
        datapath.send_msg(out)
